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7 Series - E38 (1995 - 2001)

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  #1  
Old 07-13-2013, 09:35 AM
KWKDRAW KWKDRAW is offline
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Location: Mohave Valley ,AZ
 
Join Date: Oct 2012
Posts: 24
Mein Auto: 97 528i , 01 740i Sport
01 740i rough start and misfire

i have recently purchased a 01 740i sport car runs great fast ..its sweet!!
a couple of weeks ago in the am 1s start of the day it ran rough i taped the throttle a couple of times and it smoothed out and ran fine the rest of the day so in the am every 1st start i would just tap the gas a couple of times and no problem no check light nothing the other day i noticed once i got off of work it did it again now its when the car sits for a few hours i.e. over night or at work while sitting for 4 to 8 hours
i when home and put my scanner on the car and found multiple misfires and misfire on cyl 3n so i swapped the coil pac 3to 4 cleared the code and took it for a spin i jumped on it trying to get it to fail on it hard several times came back checked the code and again multiple misfires and misfire on cyl 3 i am not sure where to go next could the plug to the coil pac be bad?
if so can it be swapped wit another for testing purposes?
Please help
Thanks in advance
KWKDRAW
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  #2  
Old 07-13-2013, 07:34 PM
Mayorchuck Mayorchuck is offline
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Location: Farley, MO
 
Join Date: May 2013
Posts: 731
Mein Auto: '96 740iL
If you changed the coil and the code did not follow, it's not the coil. Symptoms sound more like a vacuum leak. Plastic, rubber, gaskets, etc. are more stiff and rigid when they are cool. Once the engine warms up and everything expands, leaks are sealed up. Very common on this car.



Any oil in the plug ports? VCG's often leak on the inside and can pool in the plug ports and over time get down into the firing area of the plug. If not leaks are found (be sure to test this when car is cold) I would check the plug ports for oil.
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  #3  
Old 07-13-2013, 08:04 PM
KWKDRAW KWKDRAW is offline
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Location: Mohave Valley ,AZ
 
Join Date: Oct 2012
Posts: 24
Mein Auto: 97 528i , 01 740i Sport
Thanks for the reply their was hardly any oil where the plugs are but i did wipe what was their up and it hasn't returned
i will give this a try in the am and give an update
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  #4  
Old 07-15-2013, 10:23 AM
KWKDRAW KWKDRAW is offline
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Location: Mohave Valley ,AZ
 
Join Date: Oct 2012
Posts: 24
Mein Auto: 97 528i , 01 740i Sport
I started up the car in the am and used break cleaner trying to find a leak ether their is no leak or i did not do it correctly

i pulled the plug and noticed it was a single ground autolite plugs...?
so i went down to the local auto parts and ordered the stock NGK dual ground plugs
do you think the extra ground would make the difference??

any ideas are greatly appreciated
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  #5  
Old 07-15-2013, 12:41 PM
JasonSC540ia JasonSC540ia is offline
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Location: Alamogetto NM
 
Join Date: Aug 2009
Posts: 676
Mein Auto: 1999 740i
Currect ones are 4 ground NGK's. When I first got my current 740i I went to swap plugs and went cheap and got 2 ground NGK's. They worked but there was a noticable loss of low to mid-range torque. I swapped the old 4 grounds back in and everything was fine.
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  #6  
Old 07-15-2013, 07:21 PM
Mayorchuck Mayorchuck is offline
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Location: Farley, MO
 
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Mein Auto: '96 740iL
Did you clear the codes after changing coils and driving it again?
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  #7  
Old 07-15-2013, 09:08 PM
KWKDRAW KWKDRAW is offline
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Location: Mohave Valley ,AZ
 
Join Date: Oct 2012
Posts: 24
Mein Auto: 97 528i , 01 740i Sport
yes i have a peak and clear the codes after every try
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  #8  
Old 07-20-2013, 05:14 AM
NashvilleYankee NashvilleYankee is offline
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Location: Nashville, TN
 
Join Date: Jul 2013
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Mein Auto: 740iL
I had a similar problem with 740iL model. Test the Oil Separator Valve in the back of the intake manifold. The OSV has a connection to a breather pipe to the air intake that connects to the inside of the engine. A good way to test is to look for vacuum leaks at the back of the intake manifold. Also, you can uncap the oil cap while the engine is running and feel if there is a vacuum.

This engine is amazingly designed and engineered. I love this car more every time I work on it (working backwards HUH ). I think the function of this OSV is to allow the air inside of the engine block to expand with change in temperature while separating the air from oil. There is a pipe that runs from the front of the engine to the back of the intake manifold and connects to the OSV. Then the OSV has a breather plastic pipe that runs through the intake (I don't like this part) to the front then connects to air intake.

If this turns out to be the problem and you have to take the intake manifold out, I suggest that you check all rubber seals, fuel injectors, and rubber coolant system hoses at the back of the intake manifold. By the way you can try to take the manifold out without missing with the fuel injectors they can be taken out as a whole. I discovered that after I did mine, next time (I hope not) I will try that.

After visiting several mechanics who told me that I am getting oil on the plugs from the valve seals and I will need an engine rebuild, I fixed it my self. I drove to that mechanic who quoted me for $4000 and revved the engine to 6000 rpm at his shop and got my money back that he took for diagnosis.
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  #9  
Old 08-13-2013, 08:19 AM
KWKDRAW KWKDRAW is offline
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Location: Mohave Valley ,AZ
 
Join Date: Oct 2012
Posts: 24
Mein Auto: 97 528i , 01 740i Sport
Changed the plugs and the OSV in the back of the manifold no more rough start
Thanks to all that helped
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  #10  
Old 08-13-2013, 09:16 AM
JasonSC540ia JasonSC540ia is offline
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Location: Alamogetto NM
 
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Mein Auto: 1999 740i
Good job! Glad to see you got it sorted.
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  #11  
Old 08-13-2013, 11:21 AM
First740il First740il is offline
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Location: michigan
 
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Posts: 106
Mein Auto: 740il
Re: 01 740i rough start and misfire

I bet it was just the plugs!!!

Sent from BimmerApp mobile app
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  #12  
Old 08-13-2013, 11:32 AM
KWKDRAW KWKDRAW is offline
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Location: Mohave Valley ,AZ
 
Join Date: Oct 2012
Posts: 24
Mein Auto: 97 528i , 01 740i Sport
The Diaphragm in the OSV was Torn
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